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+---
+name: ubiquitous-language
+description: Extract a DDD-style ubiquitous language glossary from the current conversation, flagging ambiguities and proposing canonical terms. Saves to UBIQUITOUS_LANGUAGE.md. Use when user wants to define domain terms, build a glossary, harden terminology, create a ubiquitous language, or mentions "domain model" or "DDD".
+---
+
+# Ubiquitous Language
+
+Extract and formalize domain terminology from the current conversation into a consistent glossary, saved to a local file.
+
+## Process
+
+1. **Scan the conversation** for domain-relevant nouns, verbs, and concepts
+2. **Identify problems**:
+   - Same word used for different concepts (ambiguity)
+   - Different words used for the same concept (synonyms)
+   - Vague or overloaded terms
+3. **Propose a canonical glossary** with opinionated term choices
+4. **Write to `UBIQUITOUS_LANGUAGE.md`** in the working directory using the format below
+5. **Output a summary** inline in the conversation
+
+## Output Format
+
+Write a `UBIQUITOUS_LANGUAGE.md` file with this structure:
+
+```md
+# Ubiquitous Language
+
+## Order lifecycle
+
+| Term | Definition | Aliases to avoid |
+|------|-----------|-----------------|
+| **Order** | A customer's request to purchase one or more items | Purchase, transaction |
+| **Invoice** | A request for payment sent to a customer after delivery | Bill, payment request |
+
+## People
+
+| Term | Definition | Aliases to avoid |
+|------|-----------|-----------------|
+| **Customer** | A person or organization that places orders | Client, buyer, account |
+| **User** | An authentication identity in the system | Login, account |
+
+## Relationships
+
+- An **Invoice** belongs to exactly one **Customer**
+- An **Order** produces one or more **Invoices**
+
+## Example dialogue
+
+> **Dev:** "When a **Customer** places an **Order**, do we create the **Invoice** immediately?"
+> **Domain expert:** "No — an **Invoice** is only generated once a **Fulfillment** is confirmed. A single **Order** can produce multiple **Invoices** if items ship in separate **Shipments**."
+> **Dev:** "So if a **Shipment** is cancelled before dispatch, no **Invoice** exists for it?"
+> **Domain expert:** "Exactly. The **Invoice** lifecycle is tied to the **Fulfillment**, not the **Order**."
+
+## Flagged ambiguities
+
+- "account" was used to mean both **Customer** and **User** — these are distinct concepts: a **Customer** places orders, while a **User** is an authentication identity that may or may not represent a **Customer**.
+```
+
+## Rules
+
+- **Be opinionated.** When multiple words exist for the same concept, pick the best one and list the others as aliases to avoid.
+- **Flag conflicts explicitly.** If a term is used ambiguously in the conversation, call it out in the "Flagged ambiguities" section with a clear recommendation.
+- **Keep definitions tight.** One sentence max. Define what it IS, not what it does.
+- **Show relationships.** Use bold term names and express cardinality where obvious.
+- **Only include domain terms.** Skip generic programming concepts (array, function, endpoint) unless they have domain-specific meaning.
+- **Group terms into multiple tables** when natural clusters emerge (e.g. by subdomain, lifecycle, or actor). Each group gets its own heading and table. If all terms belong to a single cohesive domain, one table is fine — don't force groupings.
+- **Write an example dialogue.** A short conversation (3-5 exchanges) between a dev and a domain expert that demonstrates how the terms interact naturally. The dialogue should clarify boundaries between related concepts and show terms being used precisely.
+
+## Re-running
+
+When invoked again in the same conversation:
+
+1. Read the existing `UBIQUITOUS_LANGUAGE.md`
+2. Incorporate any new terms from subsequent discussion
+3. Update definitions if understanding has evolved
+4. Mark changed entries with "(updated)" and new entries with "(new)"
+5. Re-flag any new ambiguities
+6. Rewrite the example dialogue to incorporate new terms
+
+## Post-output instruction
+
+After writing the file, state:
+
+> I've written/updated `UBIQUITOUS_LANGUAGE.md`. From this point forward I will use these terms consistently. If I drift from this language or you notice a term that should be added, let me know.